The light on the history of OLED materials and technology. From inception to modern innovations.
OLED (Organic Light-Emitting Diode) technology has revolutionized the display industry, offering brighter colors, deeper blacks, and more energy efficiency compared to traditional display technologies. These are the reasons behind the fact that the biggest technology manufacturers invest significantly more in the development of their products than entire countries do in R&D. 35 years after developing the first practical OLED device, the global OLED market size was estimated at USD 38.44 billion and is expected to be worth around USD 259.67 billion by 2032 (source). What is the history of this fast-growing technology? Let’s find out.
The early days of OLEDs
The story of OLEDs we know today begins in the late 20th century. In the 1980s, researchers discovered that organic materials could emit light when subjected to an electric current. This was a breakthrough, as it laid the foundation for the development of OLED technology. In 1987, Kodak’s chemists, Ching Wan Tang and Steven Van Slyke, developed the first practical OLED device (source). Their work demonstrated the potential of OLEDs to produce light with high efficiency and brightness.
This undoubted industrial achievement was preceded by over 20 years of academic research. It started in 1961 with the discovery of the first evidence of thermally activated delayed fluorescence (TADF) in a fully organic molecule using the compound eosin. (source)
The evolution of emitter technologies
As OLED technology progressed, the focus shifted to improving the efficiency and color purity of the emitters – chemical compounds that emits light upon application of electricity. They are a vital part of any OLED display and determine its parameters of color, contrast, lifetime.
Today, the development of emitters over the years can be demonstrated by showing the progress of successive generations of emitters, each bringing significant advancements.
First-generation emitters
First-generation OLEDs used fluorescent emitters. While they were a breakthrough, these emitters had a major drawback: only about 25% of the electrical energy was converted into light, with the rest wasted as heat. This inefficiency limited their practical applications and lifespan.
Second-generation emitters
The second generation saw the introduction of phosphorescent emitters. Unlike fluorescent emitters, phosphorescent materials could achieve nearly 100% internal quantum efficiency. This meant almost all the electrical energy could be converted into light, significantly improving the brightness and energy efficiency of OLED displays.
Even though phosphorescent emitters offer high efficiency and potential for application in OLED technology, the presence of expensive and toxic rare earth metals and precious metals in the structure of complexes causing problems with recycling, limit their application on an industrial scale. Moreover, to date, there has been a notable lack of blue emitter, that represents 70% of display light emission, of second generation.
Third-generation emitters: the rise of TADF
Remember 1961 and the first evidence of TADF? Third-generation emitters introduced this groundbreaking technology. TADF materials combined the benefits of both fluorescent and phosphorescent emitters. They utilized a mechanism that allowed the energy from non-emissive triplet states to be harvested and converted into light, greatly enhancing efficiency. TADF emitters provided a path to achieving high efficiency without relying on rare and expensive heavy metals, which were essential for phosphorescent emitters.
Fourth-generation emitters
Fourth-generation emitters build upon the principles of TADF but introduce hyperfluorescence. Hyperfluorescence combines TADF materials with highly efficient fluorescent dopants. This synergy allows for even higher efficiency and color purity, pushing OLED performance to new heights. Hyperfluorescence emitters are paving the way for more vibrant and energy-efficient displays, marking a significant milestone in the evolution of OLED technology.
Fifth-generation emitters
The development of emitters doesn’t end on fourth generation. Noctiluca develops not only third and fourth, but also fifth-generation emitters. In January 2024, our company filed a patent application for our latest breakthrough: fifth-generation OLED emitters based on Phosphorescence-Sensitized Thermally Activated Delayed Fluorescence (PST), marking a significant advancement in the field.
Applications and impact of OLED technology
Thanks to years of R&D work of great scientists and producers OLED displays have become ubiquitous in modern electronics, finding applications in smartphones, televisions, wearable devices, and more. The flexibility and thinness of OLED panels have enabled innovative design possibilities, such as foldable and rollable displays. Additionally, OLEDs are used in lighting solutions, offering energy-efficient and aesthetically attractive alternatives to traditional lighting technologies.
Progress in OLED technology
Source: Rep. Prog. Phys. 86 (2023) 096501
The advancement of OLED technology, particularly the development of new emitter materials, has had a great impact on the display industry. The continuous improvement in efficiency, color purity, and lifespan of OLED displays has set new standards for the entire industry. These factors combined with lower and lower cost of production and in a result affordable price on a store shelf, has made OLED the preferred choice for high-end consumer electronics.
The history of OLED displays proves the power of innovation and collaboration in the field of material science and engineering. From the early days of fluorescent emitters to the cutting-edge hyperfluorescence and PST technology, each generation of emitters has brought significant advancements, driving the widespread adoption and evolution of OLEDs. As research continues and new materials are discovered, the future of this technology promises next exciting developments.
Source [apart from mentioned in the article above]:
- “Generations of OLED emitters”, Piotr Trzaska, PhD, Noctiluca link
- Advanced Materials 2021, A Brief History of OLEDs—Emitter Development and Industry Milestones, Gloria Hong, Xuemin Gan, Céline Leonhardt, Zhen Zhang, Jasmin Seibert, Jasmin M. Busch, and Stefan Bräse